There are various environments in which self contained portable fluid samplers are useful. For example, it is often desirable to monitor ambient air for contaminants and to obtain samples which enable the detection of even minute quantities of such contaminants. Such devices should be relatively small and lightweight so that they can be readily transported from one location to another. They are useful in industrial applications such as in chemical plants and the like where workers face a potential exposure to airborne toxic substances over prolonged periods of time. Another environment in which portable samplers may be employed is in mining operations. Yet a further use of such samplers is in space-craft programs where it is desirable to collect composite samples over periods of time in order to determine the exposure of the crew to contaminants within the space-craft cabin.
One type of portable air sampling monitor is disclosed in U.S. Pat. No. 4,080,832 to Moody et al. In the monitor disclosed in this patent, a bellows is provided which is collapsed and expanded by a motor under the control of a clock pulse circuit. Each time the bellows is expanded, it acts as a suction pump to draw air in through a filter. The clock pulse circuit is programmed to operate the bellows at a desired frequency, e.g., once every minute, during a desired interval of time such as the workshift of an industrial worker. The logic circuitry associated with the air sampler counts the number of times the bellows is pulsed during the sampling interval so that the total air volume flowing through the air filter can be calculated. At the end of the sampling interval, the filter is removed and analyzed to determine the identity and quantity of the material trapped in the filter. From this and from the logic circuit parameters, the contaminate concentation in the air can be determined.
U.S. Pat. No. 4,091,674 to Amey discloses an air sampling pump for use in air monitoring systems. In this reference, the pump is disclosed as a bellows-type suction pump mounted on the exhaust side of a collector tube so that the pump operates to pull sample air through the tube. Means are provided in Amey to carefully monitor the operation of the pump so that air flow through the sample tube can be accurately measured.
Yet another air sampling device is disclosed in U.S. Pat. No. 3,540,261 to Scoggins. In Scoggins, a circular magazine is mounted within a cylindrical housing for rotation about the axis of the housing. The housing is provided with a sampling port in the cylindrical wall thereof. A plurality of samplers are mounted around the periphery of the magazine in a uniformly spaced relationship. The magazine is then rotated to bring each of the samplers into engagement with the air monitoring port for desired collection periods which can range from five minutes up to twenty-four hours. Each sampler includes a sampling medium secured within a housing. A vacuum conduit or passage extends rearwardly through the housing so that upon exposure of the sampler to the atmosphere through the sampling port, air can be drawn in by means of a suitable vacuum source.